Strange creatures on mint leaf

Observation - Strange creatures on mint leaf. Description: Two strange creatures, each about 8-10mm long. Green, spiky, with slimy black attachments on their backs. Legs underneath with started to crawl when I touched the creatures, so the spikes aren't legs. Small, grey slimy worm-like thing also started to m

Two strange creatures, each about 8-10mm long. Green, spiky, with slimy black attachments on their backs. Legs underneath with started to crawl when I touched the creatures, so the spikes aren't legs. Small, grey slimy worm-like thing also started to move from the things on their backs. Horrible.